A projection system is a device capable of presenting still and/or motion video signals from a light source of a light emitting device to one or more viewers by projecting the signals on a front or a rear surface of a screen.
The projection system may be categorized into four types based on operation methods, that is, a CRT (cathode ray tube) method, a DMD (digital micro-mirror device: a trademark of Texas Instruments) method, a reflective liquid crystal panel method, and a transmissive liquid crystal panel method. The LED (light emitting device) is on the increase as a light source for the projection system because of its small physical size, low-power consumption, long lifetime and availability of three primary colors.
The projection system is recently miniaturized for portability. However, the portable projection system has a disadvantage of limited time of use due to reliance on battery for power supply.